Jamie Taggart, of Cove, Argyll and Bute, left his boarding house in Sa Pa Town to go plant-hunting on November 1 but did not return from the trip in the northern mountainous region.
Vietnam-based travel organiser Phil Hoolihan, speaking from Sa Pa, said that while it was unlikely, it was possible the 42-year-old could have survived in the remote jungle area despite severe conditions.
He said: "There is food available. There are caves and there are areas where shelter can be found. And the local tribes who use the forest for hunting do spend a great deal of time up there at certain times during the year.
"In all honesty, it will be difficult to survive up there and I think the search party are aware of that but there is still hope and that is why they are still looking to find Jamie alive."
He added that "when you are looking at the type of people that could survive for a great period, it's someone with a knowledge of the local flora and fauna, which I know that Jamie was very knowledgeable of".
Mr Taggart runs Linn Botanic Gardens in Cove on the Rosneath peninsula and serves as a retained firefighter.
He planned to document high altitude plant specimens and it is thought he went missing somewhere in or around the Hoang Lien National Park.
Another report from the local searchers is that based on the findings, Mr Taggart may have taken public transport in the direction of Lai Chai Province, and searches in the Ban Khoang Mountain area have been carried out.
Freak snowfalls hampered searchers in December and the hunt was halted during Chinese New Year before trekking in some parts of park was banned because of risk of forest fires.
The heavy snow in the province damaged numerous large trees and tourist routes and as the plants withered, the fire risk increased.
Friends and family have been fundraising for the searches and the reward for finding Mr Taggart has been doubled.
The Cove community has raised thousands of pounds thorough various fundraising events and brought in a further £1000 this week, with a screening of Sunshine on Leith, the film based on songs by The Proclaimers.
The national park region, with about 2024 and 327 flora and fauna varieties respectively, is a key eco-tourism spot in Vietnam.
Mr Hoolihan said: "They have been searching on and off, weather dependent, for the last few weeks and they intend to continue their search and narrow the field of where Jamie is thought to have walked into."