When you arrive in the Kingdom make sure that the immigration officer has stamped your visa with the correct number of days that you are entitled to on your visa. It’s difficult to sort out later.
All visitors arriving by plane automatically get 30 days without any other type of visa.
Take my case last winter. I went to Mai Sai and I had a four month visa . I should have had 60 days left before leaving but when I checked it was only 45. I brought it to the attention of the officer. His superior, a woman took it and made the adjustment and handed it to me.
Recently, a retirement visa holder told me that she had not checked her Visa when she entered . They had given her the usual 30 day visa upon entry by plane. Yes, it got sorted out but only with a lot of effort later as she did not catch it upon entering.
I was given this tip last year by a kind gentleman who was living at the same guest house as I.
If you have to do a Visa run to Mai Sai near the Burmese border, I highly recommend the Green V.I.P bus. It is either a 18 or a 24 seat full size bus. This arrangement gives you a lot of space in your seat. You also choose your seat and there is a row of single seats if you are traveling alone. The buses may not be the most up to date but the space on this 12 hour journey -from the time you leave to the time you return- is worth the couple of extra dollars. I would recommend packing a decent healthy lunch the night before as the bus stops for only 15 minutes and there is virtually nothing to eat on the journey .You will be given a lunch of sorts with a drink each way but you will want more and perhaps a different kind of food if you are health conscious.
If you go to Vientienne,Laos, the overnight mini bus is good choice.
The tuk tuk drivers in Laos are very expensive.