Rosetta stones doesn't have Thai. There are a few apps that can teach Thai that are alright, I think Ling is the most recommended.. But it seems in my personal experience these apps all fall short. Going to a class, even online is probably much better, and there not too expensive.
All covid requirements were pretty much dropped. However, 99% of residents still wear masks (Bangkok) . Only foreign tourists do not. Some establishments still require a mask.
You should actually say, cook food for your Thai girl...That might be more of a thinker. For oneself no question.. But technically do something for other is generally illegal. I seen problems in Canada about boyfriends helping do big projects around the house get in trouble with immigration.
The definition of "work" by immigration is not solely attached to income. There are many kinds of work that require the proper visa and work permit even if unpaid.
The Thai government has mentioned they allow travel youtubers to make content on Thailand on tourist visa as long as it is part of a larger trip...but if it is solely on Thailand then they would require a work permit.
I would say it's probably a grey area.. If the content has anything to do with Thailand it could be a black area... But realisticly I would not worry that much of immigration coming knocking at your door unless you do something stupid.
As long as it is a legitimate visa, it's okay. I did the same thing this past year and switched inside Thailand. There is no obec document like elite tells you.. The only thing you need is a letter from your school to cancel your visa.