"The biggest thing I want to achieve," she said, "is being able to sustain this – to keep going the way artists used to when they'd make 10, 12 or even 15 albums in a lifetime. I want to be able to do that and do it successfully for the rest of my life."
Six years and six months later, Thom would seem to have no worries on that score, not least because she has just released, to excellent reviews, her fourth studio album. It is a remarkably assured piece of work. In a sense, her three previous albums – Smile: It Confuses People, Pink & The Lily, Merchants and Thieves – have all led up to Flesh and Blood, in the sense of a maturing musical sensibility and broadening subject matter.
Her career has taken off, too: she has, in her own words, "played everywhere from huge 40,000-capacity stadiums in Scandinavia with George Michael to a tiny blues club in London". She also has a flourishing record label, Guardian Angels, and her personal life is everything she could have asked for.
Thom now lives in Malibu, California, a strikingly beautiful place 50 miles north of Los Angeles, fringed by mountains and coastline. "I wish," she said recently, "I could communicate to people what a beautiful part of the world it is."
She lives with her partner Joe Bonamassa, the virtuoso blues guitarist. She got her Green Card this summer but cannot apply for citizenship until she has lived in America for five years. One of the strongest tracks on her new album is Love You Like a Lunatic: no prizes for guessing who it's about.
Thom, who was born in Banff 31 years ago and was raised in Macduff, met Bonamassa a few years ago when he lost his voice while on tour and found himself in urgent need of a singer. Thom got the call, they met up. She learned the songs in his set-list. And something clicked.
"I moved to Malibu because that's where my life went, that's where my love went. I followed my heart. It wasn't through any burning desire to leave Scotland. But I love living there.
"I don't actually take part in the whole Hollywood scene, but living out there is like living with the elements. We live right on the sea. It's amazing ... you wake up in the morning and dolphins swim by. It really gives you a new outlook on life; it puts things in perspective.
"It also makes you feel quite humble. Living so close to the Pacific and seeing life at its rawest can really connect you to the elements and make you realise how small you are. I love living there. It's a great place for a musician, it's very inspiring. It can chill you out – that's probably why most people go there – but at the same time you have businesses to run. Guardian Angels is still my responsibility, no matter where I am. But I like the contrast between a life that's chaotic on the road and a personal life that is really peaceful and quiet.
"The label is going well, too," she adds. "It's pretty much like building a house. You have to lay the foundations, and that's what I've been doing over the last year. When I secured a distribution deal with Fontana Universal it was one of my biggest achievements in life; deals like that aren't exactly handed out on a plate. The company president really believed in my enthusiasm in building this mini-empire. It's still at its teething stages but I hope it can become a great place for a lot of artists."
Thom is happy with the critical and public reaction to her album, which was recorded in Nashville and produced by Rich Robinson of The Black Crowes. Of its 12 tracks, she is particularly drawn to The Big Ones Get Away, a politically charged song written by Buffy Sainte-Marie, a Canadian Cree Indian singer-songwriter who has found herself in and out of fashion over the years, but whose songs have been covered by everyone from Elvis Presley to Courtney Love.
"You wouldn't have expected me to end up covering a Buffy Sainte-Marie song," says Thom, struggling to make herself heard on her phone above the cacophony of a London Starbucks ("people are asking me questions and I'm like, 'Can you not tell I'm doing an interview?') "But my mum introduced me to her when I was young. For me, Buffy embodied that rock chick ethic – she had huge amounts of passion and belief in what she does, and I always found that inspiring.
"I always wanted to cover that song, it's always been a personal favourite. We recorded my version in Nashville and went about trying to see if I could find her. We found out she was living in Hawaii. I sent her my version and she loved it, and she ended up working with me on it. It was amazing."
The new album almost seems to come across as a personal liberation for Thom. "Working with different people, working with Rich, and not having the same producer or the same band as before... all of that really allowed me to put a lot of myself into the mix. I had worked with the same people on my first three records, one of whom was my ex-fiance [musician Jake Field], and my breaking away from all of that and starting again, really cleaning the slate personally and professionally, meant I could let my influences come through on the record.
"When I listen back to it, I can really start to hear myself, which is great. This is my fourth album, and people take a lifetime trying to stumble upon a sound they have been homing in on. It's something you just carve out – it's not premeditated or anything like that. It has taken me a little while to define what my sound is. It's like what some people have said about the album: it's like a cross between blues, rock, folk, country and pop. That's true. All of these different genres have influenced me."
AS far as keeping in touch with her her fans is concerned, Thom maintains a high profile on social media and her website offers a succession of behind- the-scenes "webisodes" and videos of her covering such songs as Guns 'n' Roses' November Rain ("that has gone down a storm") and the plaintive Nine Inch Nails classic Hurt.
"Now, more than ever, it's about having a relationship with people as much as you can," she says. "That's the nature of the business these days. It's not about being an aloof or elusive star ... it's about being up close and personal. That's what people desire; you need to have a relationship with them. Music is so obtainable now, and in order for somebody to take the time to buy your records, you have to earn that right."
There's enough of the music fan in Thom to make her recount with excitement her recent Royal Albert Hall charity show with such musicians as Brian May, Alice Cooper, Bruce Dickinson and Led Zeppelin's John Paul Jones. When she sang November Rain, May exclaimed in surprise: "I had no idea you could sing like that ... You're the real deal!"
As working musicians, Thom and Bonamassa are not exactly under each other's feet seven days a week. Sandi, back on the road, has played some shows on the continent and is now on the British leg, with three dates in Scotland. She has promised a "pretty special" DVD shoot in Scotland towards the end of November. Ahead of her, once the New Year is out of the way, lie a number of concerts in Australia.
Bonamassa is renowned as one of the hardest-working guitarists on the circuit. The veteran of many hundreds of concerts, he has also returned to the road, tweeting last week: 'Last day at home for a few months. Packing and making sure I don't forget any lights on. I would come home to a 30,000 dollar electric bill.'
Beyond that, a return to Malawi is a possibility for Thom. One track on her new album, Sun Comes Crashing Down, was inspired by a visit she made to that impoverished but beautiful country in southern Africa. Its annual Lake of Stars music festival has attracted many big-name acts. "Funny you should mention Malawi," she says. "We were talking about it just last night. We'd like to go back, and might just end up playing the festival next year."
Sandi Thom plays King Tut's in Glasgow on Saturday November 10, Lemon Tree in Aberdeen on Sunday November 11, and the HMV Picture House in Edinburgh on Monday November 12. Further info: www.sandithom.com or www.ticketmaster.co.uk