In custody are three Indonesian nationals, one Filipina, one Nigerian and one Niger national.
Officials of the Office of the Narcotics Control Board (ONCB) began following the gang after receiving a tip-off that they were waiting for a drug delivery ahead of the Songkran festival. The arrest took place on Wednesday, ONCB chief Pongsapat Pongcharoen said on Friday.
The operation started with the capture of Nanang Suhendra, a 37-year-old Indonesian man, immediately after he picked up a package at TTI Intertrade. Authorities found 530 grammes of "ya ice" concealed in two glass vases.
The arrest led to a raid at a hotel in the Ramkhamhaeng area later and five more people were captured.
Arrested were Indonesian women Itee Jelanee, 38, and Habibee, 57; Camelle May Aquino, 29, of the Philippines; Ogole Eseou, 35, of Nigeria; and Hassane Maman, a 32-year-old man from Niger.
Authorities also found another three kilogrammes of crystal methamphetamine hidden in a bag and 49 condoms filled with white powder.
Pol Gen Pongsapat said the powder-packed condoms were used by smugglers to rehearse ways to conceal drugs by swallowing them.
Officers also seized a list of 12 people, Thais and foreigners, suspected of being the gang's accomplices.
Those on the list were being trained so they could go to China to pick up drugs and bring them to Thailand.
The seized drugs originated in Guangzhou, the ONCB chief said.
The six conceded that the plan was to sell the drugs to tourists and Songkran revellers in tourist spots in Bangkok, including Khao San Road and Soi Cowboy.