It depends on circumstances but wondering how long it might take to get a visa on arrival in Krabi airport in November?
For avoidance of doubt, I presume you're referring to the paid visa on arrival service for Chinese, Indian and some other nationals, not the visa-free option for most ASEAN and EU nationals.
So the answer is... it depends. If there's no line, you can get one in minutes, but the line length depends on how busy the airport is with arriving flights, how many of those visitors need visas on arrival (most don't, but Chinese do and there are lots of flights from China to Krabi) and even where you're sitting on the plane.
In general, though, Krabi is operating well above capacity and you can expect to queue both coming and going: we spent over an hour in line both ways last January, and we didn't even need visas.
Visa on Arrival (VoA) vs Visa Exempt (VE)
Just to clarify, if you do not get a visa in advance, there are 2 major programs you can enter into Thailand:
VE: No cost and most countries get either 15 or 30 days per entry.
There is also a Bilateral Agreement. Similar to the Tourist Visa Exempt program, but amount of time ranges from 14-90 days per entry.
VoA: You get 15 days and there is a fee for this (2000 baht?), and it is issued at the border immigration, usually in a line dedicated for VoA. Not sure about which land borders do it, but all of the int'l airports should. Lithuania qualifies for VoA. You need 1 passport size photo 4cm x 6cm. They should have some private booth nearby that will do it for a small fee, but I wouldn't rely on that.
Also, you cannot extend the VoA for additional time. You must exit and enter again for another VoA or get a visa prior to arrival.
Money show requirement: Usually not too strict if you already have a visa. It is 10,000 THB equivalent (for VE) or 20,000 baht per person for most other visas. If you don't go too often, it should be fine. But technically they can ask for it, usually on suspicion that you are working illegally (usually indicated by several VEs in close proximity of each other). I wouldn't worry about it too much.
Depends on the queue for immigration arrivals. There were recent reports of people having to wait upwards of 4 hours to get stamped in at some airports. This isn't all the time, but I would allow 90 minutes. You can apply for fast-track service, but that may only be limited to BKK airport only.
It might be cheaper to get a SETV from Thai consulate where you are now prior to flying over. SETV would give you 60 days plus option to extend at local immigration for 30 more days (1900 baht).