Mark Robson, 27, had been holidaying on Phuket and last used a card at an ATM on Phuket on January 23.
Phuket Tourist Police have been asked by Mr Robson's mother Merneen to make further inquiries and to seek public help in tracing her brown-eyed, brown-haired son.
Mr Robson moved from the Old Phuket Hotel in Karon, where he was joined by his parents for a week, to Nai Yang, a beach village south of Phuket International Airport, about January 12-14, his parents believe.
''His last e-mail was on the January 15 from Nai Yang Beach,'' his mother wrote in an email to Phuket Tourist police officer Frank Tomenson. ''We have not heard from him since.''
She added that her son hired a motorcycle for the day on January 14. Mr Robson had stayed in Bangkok, on Samui and Phangan island then stayed in Patong on Phuket before joining his parents for a week in Karon.
''We received a call from his employers in Taipei to say he had not arrived,'' the email said. ''He was due to start teaching English on February 8 on a year's contract.''
Mr Robson said her son was always diligent in letting his parents know about where he was staying but had sent no word about his accommodation in Nai Yang.
He was travelling on a British passport but also holds a South African passport.
A 'MISSING' poster advises people who may have information to contact Cathy Robson on +27 834 271218 E: firstname.lastname@example.org or Jess +27 828 970707 E: email@example.com