that makes sense, as 3 years is quite a bit longer that 183 days. By law, he owes tax on his income earned while in the country, whether it's sourced domestically or not.
this is an interview released a couple of days ago with the Deputy Director General of the Consular Section of the Ministry of Foreign Affairs about the news visas, with a focus on DTV. You might want to have a look.
you can apply to a visa in Thailand from any country other than Thailand just by being there. I've done that myself when I wanted to spend 6 months in Thailand and only had 60 days. I went to Penang nearby to get a visa to re-enter, it's what everyone that lives in Thailand constantly without a long-term visa does.