I can't say that I have had this experience. The day I arrived and left have to the best of my knowledge and calculations always been counted in my 30 now 60 days.
It was 500 baht from AIS in their Future Park store. True next door could only offer me a one month plan for over 1000 baht! I only wanted a one month SIM. AIS also had a 2 week SIM for around 300 baht.
Well if it's the weather you're after, my advice would simply be to avoid April and May. I am in Bangkok now and the skies are largely grey and the temperature not too hot. Rain is intermittent but rarely heavy. I have the aircon turned off in the room much of the day and evening. There's still something not ideal about it but it beats being in Melbourne.
Also if you arrive at night, you just want to get quickly to your hotel. I would only take the train in the daytime or if I was taking only one train to my hotel. I have never been charged for luggage and never been cheated by a taxi driver.
If true it's crap. If you're Russian you get 3 months visa free entry. I'd be buggered if I would be getting a visa 4 months ahead of time with all the other strings attached to visa approval.
I can imagine you joining the line for BTS tickets in your bikini and sunnies, with your towel draped over your shoulder as you flip-flop your way to the platform to catch your train to the beach. (Sorry - just realised you're a bloke!). I am going to give Hua Hin a try this time after a couple of weeks in Bangkok. I think you'd be happier there too. It's the rainy season so you might be spending a lot of time indoors.