If I have non-immigrant B visa for 90 days and want to stay 1 month longer (not working, just travelling) what is the best way to do it without leaving the country? Also, did anybody do this type of visa in Hanoi recently? Do I need any original document or printed scan should be okey?
TLDR : Answer Summary
To extend your non-immigrant B visa for an additional month without leaving Thailand, it is advisable to perform a border run, for example, to Myanmar, which is approximately a 4-hour drive from Bangkok. Make sure to check the entry requirements for your nationality, as you may receive a different duration of stay upon re-entry (either 30 or 15 days). Alternatively, extending the visa beyond one year requires certain documents from your employer, and you would need to visit an Immigration Office with the required paperwork.