@J**
, yes there is a limit :/ BUT each consulate decides the limit for that consulate. Then they red stamp you stating you got a lot of tourist visas from them and you will be denied one if you apply again.
@Ma**
, that's a tricky question. There are reports of the thai consulate in Phnom Penh not issuing a tourist visa because the person had a red stamp from the thai consulate in Vientiane on their earlier visa. AND there are reports of someone with a red stamp from Vientiane also getting a red stamp in Penang on the first tourist visa they applied for there.