Unfortunately
@E**
you have limited options. :/ I'd say contact the thai consulate in Sweden and CHECK with them whether you can or can't get a 6 month METV. Most consulates are more concerned about the financial requirements (no matter what's written on their website).
If you can't get that you could do a single entry tourist visa from there before you came here. You could also go to thai consulates in nearby countries and get single entry tourist visas from them as well because Latvia is not on the list of countries that can't use them.