What are the visa options for staying in Thailand as a Swedish and Finnish citizen for 102 days?

Easiest is to get the 60 day visa exemption on entry then towards the end of that leave Thailand then re-enter for another 60 days.

I would say as you get the 60 days on entry the best and cheapest way is to just then do a border run and get the additional 60 days so more than your intended 102.

Don’t do an extension as you’ll only be at 90 and therefore still need to do a border run as have paid the extra 1900 for nothing whatsoever

You can enter on a 60 days visa exemption and do a 30 days extension at your local immigration, leave and re-enter on another 60 days visa exemption.

Be aware that’s it’s a formal requirement for visa exemption that you’re able to show proof of an onward ticket within 60 days even though you plan to apply for an extension later. Also when you re-enter Thailand.

So if you use visa exemptions for this stay, the best might be to buy a ticket out of Thailand within 60 days before you leave. Spend a couple of days in a nearby country and re-enter on another visa exemption with your return ticket back to Europe.

If you want to cover your whole stay with a visa you could apply for a six months multiple entries tourist visa before you leave, but you’ll still need a trip out. The one year Non O-A visa could cover all your stay, but there are several requirements and you should be fine just using the visa exemptions here.

With no visa bought prior you’d get a 60 day visa exempt stamp on arrival and can extend that once for a further 30 days at a local immigration office. Leave and re-enter after that for a repeat of 60+30.