Bangkok is currently coping with unhealthy levels of PM2.5 particulates.
On the 26th of January, the Bangkok Post wrote an article with the following passage on a link with Cambodian crop burning:
Pollution Control Department (PCD) director-general Pralong Damrongthai told the Bangkok Post that the department acknowledged there was transboundary haze from Cambodia and that he had urged the government to monitor the burning.
However, PCD air quality monitoring stations along the Thai-Cambodian border in Trat and Chachaoengsao have not detected severe air pollution in Cambodia recently.
Prof Serm Janchai, a lecturer on physics at Faculty of Science at Silpakorn University also shared the same view that "part" of the PM2.5 comes from open burning in Cambodia.
Prof Serm has conducted tests and found a correlation between open burning in Cambodia, wind direction, and the level of PM2.5 in Bangkok recently.
He said his study of atmospheric dust had found a high level of fine PM2.5, suggesting the source could be opening burning.
Other than correlation (which doesn't necessarily imply causation), what evidence is there that Cambodian crop burning contributes to the unhealthy particulate levels in Bangkok?