My previous experience doing Extension of Stay (Thai Wife) based on income proof, the immigration would require tons of corporate tax documentation from my ex-employer (a publicly listed US MNC and also a BOI entity) - I know this because the HR staff told me that she need to take bunch of pictures of the workplace and also when I went to CW for interview, I saw a pile of my employer's corporate tax filings document in the package submitted by the visa agent used by the company.
This was after having worked with the company in TH for more than 2 years (I was under Non-B initially and yes, I also had all my personal income tax filing documentation submitted alongside).
long story short.. it felt like quite a bit of a hassle, although it was prepared by someone else and I got the agent doing the waiting and all. (Very different compared to the Non-B application under BOI).
After I left to start my own company.. I mostly just go with the 400K route since I self file and it's a way more straightforward.
