I've been living and working (and paying a lot of taxes) in Thailand for several years, on One Year Multiple Entry Non-Immigrant 'B' Visas. Until today, every time I've entered Thailand I've been given a 90 Day stamp.

Today I did a border crossing and back at Nong Khai / Vientianne, but was only given a 30 Day stamp upon re-entry into Thailand. I did not notice it until after I had left Nong Khai. My Visa does not expire until July.

Did they change the rules? Or did Immigration just make a mistake? The taxi driver I hired in Udon Thani to take me to Nong Khai and back said he thinks if I had stayed overnight 1 night in Laos I would have been given 90 days, but obviously he's no expert on immigration law.

Anyone with expertise able to answer this?

Go to a immigration office to have have the error corrected.

Probably a simple error . Your local immigration office may be able to correct /------------ If not a journey back to the border will be needed.

Remember always check prior to leaving the immediate vicinity of immigration !

the warning poster in front of your eyes just when you accept documents back at immigration booth - "check your entry"

Even if you spend only 1 minute in Laos, you'll be given whatever permission to stay your passport/visa combination allows upon returning to Thailand. There is no requirement to spend any minimum amount of time abroad.