As far as Thailand is concerned, what you mention is pretty much illegal.
Although it is always absolutely possible to "slip through the cracks" in certain circumstances, know that it can all come chrashing down on you in an instant.
Remaining "Under the radar" would be my first tip.
The second tip would be NOT to announce your intentions on social media!!
fair enough! i gotta say, it puzzles me about these recent reports of guys getting turned away/hassled when going for VE's at the 2 main Thai airports.
maybe its the country you come from and errrr what kind of permanent dark suntan you might have.