While Burma had its hands full with the Ming Chinese invasions, Siam's King Narai attempted to pick off the upper Tenasserim coast and Lan Na. He got Martaban to switch sides in March 1662, and occupied the coast. Fortunately for the Burmese, their troubles with the Ming were over. Their land and naval units recaptured Martaban and Tavoy by December 1662. They followed up on the retreating Siamese but were driven back near Kanchanaburi with heavy losses. Meanwhile, a much larger Siamese army invaded Lan Na, catching the Burmese command completely off guard. The Siamese captured Chiang Mai on 10 February 1663, and drove back Burmese forces that arrived belatedly. In November 1663, Siam launched a two-pronged invasion of the Tenasserim coast: Martaban and Moulmein in the north and Tavoy in the south. Burmese defences withstood several Siamese onslaughts until May 1664 when the invaders retreated before the rainy season arrived. Meanwhile, the Siamese garrison at Chiang Mai was holed up in a deserted city, and its troops were constantly ambushed by resistance forces whenever they ventured out of the city. In late November 1664, the Siamese evacuated Chiang Mai, and returned. This was the last major war between the two kingdoms until 1760 although they traded small raids in 1675-1676, and in 1700-1701.
Question: How many months did Siam invade the Tenasserim coast before retreating?
Answer: 7