that's wrong statement. TR visa valid 90 days from issue, in your example 1 Jan to 1 Mar. On entry visa becomes used and you get a 60 day stamp, visa validity don't have any relation to permitted stay. That's exactly how all Thai visas work. METV has 6 months validity, and you get same 60 day stamp on each entry inside validity frame, even you enter on last day of visa validity