Tom Grieve, 57, a former member of the Connel Flying Club in Oban, is understood to have died from chest injuries in hospital. A passenger, 31- year-old Patrick Esser, is being treated in hospital in the resort of Pattaya for a broken arm.
The two men were taking the ashes of a recently deceased friend to be scattered over the sea when the engine of their microlight failed.
They scattered the ashes immediately then prepared for an emergency landing.
Other friends who were below on speedboats saw the microlight clip a newly constructed pier before going under the water.
Mr Esser is now recovering in Pattaya Memorial Hospital, 100 miles east of Bangkok.
He said: "My friend Stuart Long had died of throat cancer aged just 41 and we were about to scatter his ashes in the sea.
"I had done a rehearsal flight the previous day with Tom and everything went fine.
"We were at about 1000 feet when the engine cut. Tom tried several times to start it but failed.
"He was gliding it down and aiming for a large piece of concrete to land on. We must have been going about 70 mph when we clipped something.
"We went head over heels and crashed into the water upside down.
"I managed to get out and started looking for Tom then I saw him surface.
"He seemed okay but was in some pain. We were taken straight to hospital and I asked him on the way if he was okay. He did not reply, but he looked okay.
"But in the hospital medical staff desperately tried to give him resuscitation but failed. They told me he had internal injuries in his chest."
Mr Grieve was the force behind microlight flying at the Nong Prue Flying Club, Pattaya, and well-known in the international microlight community.
He learned to fly in Morpeth, Northumberland, and went on to become a leading figure in the Connel Flying Club in Oban.
John MacGilvray was chief flying instructor of the club when Mr Grieve was a member.
Mr MacGilvray, 79, said: "It's a blow to hear of another flyer being involved in a fatal accident. He visited here frequently and flew here frequently. He was a regular visiting pilot here for about five years and for a while he was here every weekend."
He added that Mr Grieve had moved to Thailand more than 10 years ago.
Mr MacGilvray said: "He had been out to Thailand on a couple of holidays and then all of a sudden he decided to join a friend who had moved there.
He added: "As far as I know Tom moved to somewhere in the north of Thailand.
"He had his own microlight and he shipped it out to Thailand when he left."
While at the Oban club he flew the "Dawn to Dusk", taking off and landing at every inhabited island in the Orkneys in one day, to receive an award from the Duke of Edinburgh.
He was very familiar with the Highlands and Islands from the air and made the first microlight flight across the North Sea from Sumburgh in the Shetlands to Hagesund in Norway, before flying down to Denmark.
He received the Steve Hunt Award in 1994 for his outstanding airmanship, then three years later won the same award again with two others for flying around the coast of Australia anti-clockwise.
An inquiry is being held into the crash.