Having acquired a Retirement visa recently the thought of not having to exit Thailand every 90 days is definitely a nice one. I need now only get a songtaew to Chonburi immigration office in Jomtien for 10 baht every 90 days instead of leaving the country. In fact, I just go to my agent's office and have a cigarette while they go and deal with it on my behalf. If I do want to leave the Kingdom I need a re-entry permit in order not to ruin the visa.
I'm guessing you have a Business visa Jim. It does seem like a pain, but I didn't think you had to exit the country every 90 days with that.
I used to enjoy my month in Cambodia every 3 months but it began to wear a bit thin after 18 months of it. Those 90 day periods seemed to come around quicker and faster as time went by.
I still like Phnom Penh though and may well take a side trip once in a while, but not for a month. From Pochentong Airport to Riverside area is a piece of cake, although costs for rides have increased now. Since New Year tuk-tuks ask for $10 within the airport compound but can still be had for $7 just outside, which is only a two minute walk away. Also, taxis are $12 instead of the old $10. I always enjoyed that tuk-tuk ride into town, it awakens the senses.