Yes.. pension earned is pre loaded onto your return virtu of clink having your TFN. As you say its under threshold so you can opt to not submit a yearly return.
There is a farang rides/drives a foodcart around every day whilst his wife (I guess)makes and sells street food. In full view of local shops, other vendors etc.2k from Pattaya in a tourist area,??
There is no one on here in your Cat 1. scenario that would be concerned so whats your point? Your 2. is probably not the average expat. either I would guess. Most would have retired, got pension then moved here 'for a long holiday',! ????