i do something similar, send the money for all the bills and food to my girlfriend and then if we go out anywhere for food or drinks I cover that from the money I send to my account.
I left for work during my initial 3 months and asked this question to the IO that dealt with my re-entry permit. She basically told me the exact thing Brandon is saying here.
Going off what I've been told by Chon Buri Immigration previously, a new TM30 is required every time you enter Thailand or change province for more than 24 hours while in Thailand.
Its really hit or miss. You could be asked by the airline before you board or by immigration in Thailand, although it's rare I've been asked in the past. If youre concerned just buy a cheap travel from Thailand to one of the neighbouring countries.
I was asked 3 entries in a row. The first time they asked for proof of accommodation for the full duration of my stay which I provided. The next entry I was asked for accommodation and a return flight. The third time I was asked for accommodation booking, a return flight and the 20,000 baht which I was able to show them. I did use to enter up to 10 times a year on visa exemptions but I never extended them. It felt like after my first questioning I had been flagged on the system and eventually they were going to refuse my entry.
it's one of the types of visa that's available in Thailand. It starts as a 90 day visa that can be extended to one year. It's based on things such as retirement, marriage or having a child in Thailand. There are other things to but if im honest I'm not sure why they all are.