Easiest is Laos. Go to Nong Khai, cross over the bridge to Laos. Cross back into Thailand and get 45 days (+30 if you extend again)

No need for a service since you'll still have to go to the consulate in person. Flight or bus to Udon Thani/Nong Khai -> $1 Green air conditioned bus from the Laos immigration to Morning Market -> overpriced tuk tuk to your hotel. (Loca App is the Lao version of Uber). Bring $40 USD in crisp bills for your Laos visa

Flying in for a visa exempt will be sketchy. I'd use an agent to do fasttrack/vip service. Or fly to Malaysia or Laos and enter by land.

If I had a bunch of covid extensions I'd get a new passport ASAP. It doesn't fix everything because immigration can still see your history, but you'll be able to get easy tourist visas in Vientiane, Savannakhet, Penang, etc.

@Otto ********

Straight to the point. I like it.

I’ve been asked multiple times most recently in May 2022

You should be fine. If they give you trouble at checkin, use an onward ticket service. Costs $12 and only takes a few minutes

There are only a few options from BKK to CNX since most of the budget airlines (AirAsia, NokAir, ThaiLion, etc) use DMK instead of BKK. I think Thai, Thai Smile, Bangkok Airways, and VietJet are the only options from BKK. Whichever Airline you choose, you'll have to clear immigration first. VietJet is the cheapest and perfectly fine for short trips.