If you don't have US Dollars you can pay in Thai Baht, but beware: they charge 1500 Baht which is a poor exchange rate. We keep a stock of US dollars here at Mut Mee for those who wish to exchange baht into dollars at a more reasonable rate
The visa is available "on the spot" on the Lao side of the Friendship Bridge, and often the wait is only a matter of minutes. However, during the busy times when the big buses go through the border in the early morning it can take quite a bit longer.
The same "Visa on arrival service" is available at Wattay Airport in Vientiane and at Ban Houi Xai across the Maekong river from Chiang Kong in the north of Thailand.
At weekends the visa price goes up by one dollar as an "overtime fee"!
The Lao Consulate in Khon Kaen gives 30 day visas only on a fast one hour turnaround. The price including an unavoidable "rush charge" is 1300 Baht approximately, but there are once again some surcharges depending on nationality.
In Bangkok travel agencies can arrange a 30 visa for you.
30 day visas are available for about 1600 Baht (possibly plus surcharges) within 4 working days. As before if you want the visa quickly you can get it within 2 working days for approximately 1900 Baht, again surcharges for nationality can apply.
But then you have to stay in or return to Bangkok to wait for your visa...
Note: Many of the travel agencies in Bangkok are telling travellers that it is not possible to obtain a 30 day visa on arrival at the Friendship Bridge, Wattay airport etc. Somtimes they say it is possible, but give an inflated price. Their aim is to sell travellers their more expensive, more time consuming service. As you can now get a 30 day visa on arrival, by far the easiest way is to not bother to get a visa in advance.
The Lao Embassy in Bangkok provides 30 day visas. These are available at the same prices as on the bridge (see information above).
Unfortunately they are located a long way out of the centre. Their address is
520/502/1-3 Soi Sahakarnpramoon, Pracha Uthit Road (End of Soi Ramkhamhaeng 39), Wangthonglang, Bangkok 10310.
In every case, except for the visa on arrival, do watch out for public holidays, these can slow you down, and remember that you will need either one or two passport photographs.
If you have no visa, most nationalities receive a 15 day entry stamp into Thailand on arrival. This is available at all entry points into Thai territory including the Thai-Lao Friendship Bridge. This entry without visa is extendible at all Thai immigration offices (there is one in Nong Khai) for another 7 days, one time only, for 1900 Baht.
You may also obtain a 60 day visa for Thailand at the Thai Embassy in Vientiane for 1000 Baht. A double entry visa is available for 2000 Baht entitling the holder to enter Thailand twice for 60 days on each entry. This takes two working days inclusive, and must be applied for in the morning only. This means that if you apply on a Monday morning you will receive your visa on a Tuesday afternoon. This kind of visa is extendible at any Thai immigration office within the Kingdom of Thailand for a further 30 days, for a fee of 1900 Baht.