Extend your visa exemption stamp (it's not a visa on arrival) and when that expires take the bus to Myanmar and walk across the border and get a new stamp. Repeat that 2 times in 2018. Cheaper than flying to Laos and get a tourist visa.
Take the Green bus (319 baht for VIP seat one way) to Mae Sai bus station and then a red truck (15 baht) to the border. Walk across and pay 500 baht or 10$ and return to Chiang Mai. It takes about 5 hours to the border.
