Gyms in Laos are generally of a reasonable standard, although often smaller than those you would find in Western society and typically with more ageing equipment. I was not aware of any chains operating in the regions I visited. English is not widely spoken to any great degree, but they will be able to communicate the price, if not displayed. Both prices and opening hours are usually displayed on the door or by reception (usually in Lao, but with numbers recognizable as prices and times!)
Average price was 10 000 – 15 000 kip, but one gym asked for 50 000 kip.
Currency approximation : US$1 = 8300 kip, €1 = 10200 kip, £1 = 11600 kip, AU$1 = 6400 kip
at the time of writing.