This card shows Mexican sunflowers on Doi Mae U-Kor, at their best in November. Achiraya, who sent this card to me, told me that these flowers bloom only once a year in the northern mountain of Thailand.
Mae Hong Son is one of the northern provinces of Thailand, and at the same time the westernmost. Doi Mae U-Kor is a hilly area there.
As for the stamps, I don't know much about the red one, apart from it being a definitive stamp and showing King Rama IX. The one on the right is from a set of 4 stamps issued in 2007, depicting Thai Temples. This one shows Wat Rajpradit Sathitmahasimaram