"dtac" is a Telecommunications company. You mean TDAC (Thailand Digital Arrival Card). That is totally unrelated to Visas or Visa Exempt entries, it's a replacement for the paper Arrival Card that used to be filled in on the plane before arriving in Thailand.
the rules don't change all the time, but they have changed the "guidelines" in November, on what extensions can be granted on Visa Exempt entries. Other than that, the only recent change was to Visa Exempt entries in July 2024, when they were extended from 30 days to 60 days and the number of countries it applied to was increased - which benefited many tourists, but Immigration has obviously seen that has been abused and so, are clamping down on that system being abused with the purpose of living in Thailand for as long as possible.
If your history of visiting Thailand clearly shows that you aren't trying to live in Thailand without a long term Visa, then there 'shouldn't' be any problems. It's always up to the Immigration Officer that you stand in front of, so nobody can really answer your question or predict what the IO will say.
they are doing something about it & that's why they announced guidelines in November, that Immigration Officers MUST follow when looking at tourist histories when entering on Visa Exempt and requesting Extensions.
age has nothing to do with the time one is allowed to stay in Thailand as a tourist. While under the guidelines announced in November this year, as long as one doesn't have a history of repeated long tourist stays, looking like they're trying to live in Thailand, Visa Exempt entries of 60 days, plus 30 day extension, and another 60 days plus a 7 day extension is possible.
Official Thailand tourism statistics show that the average tourist stays for 7-14 days. So, anyone visiting for around that amount of time would be considered a genuine tourist and would likely be allowed into the country multiple times per year.
While arrivals crowds like this will vary according to seasons - peak/off peak, blame numerous foreigners that tell people in forums like this, that TDAC can be done at the airport upon arrival, rather than telling them to do it online up to 72 hours before arriving in Thailand. Then there's people that don't check entry requirements to a country before they actually make their plans, such as flights and accommodation.