What are my options to extend a 60-day METV in Chiang Mai, and how is the validity calculated?

The user is seeking guidance on extending their 60-day Multiple Entry Tourist Visa (METV) in Chiang Mai, which is valid until December 22, and is asking whether to extend at an immigration office or do a border run to Laos. Responses indicate that they can either extend for 1,900 baht at the immigration office or do a border run to receive another 60-day stamp, with a suggestion to go to the Mae Sai - Tachiliek border for the easiest option without the need for a visa for Burma. Additionally, it is confirmed that the visa’s validity is determined by the stamp date of entry (October 24), not the issue date (October 10).