Teekhawuth Sriburin, chief of the national park, said this happened so suddenly and left park officials in a state of shock.
Mr Teekhawuth said yesterday afternoon he received a telephone call from a foreigner who told him that his son, a German tourist called Loo, had been in the Khao Ngon Nak mountain area. The caller said he was afraid Loo, who was suffering from depressive disorder, would take his own life and asked park officials to look for him, reports the Bangkok Post.
Park officials at the Thap Khaek forest protection unit checked the log book and found that Loo went out for trekking at 11:12am. The officials asked the caller to send them a photo of Loo for use in a search.
In the search, the park officials found Loo at about 5;30pm. They talked Loo into coming down to their office with them and Loo agreed.
On the way down, at about 6:30pm, after a 2 kilometres walk from the spot he was found, Loo received a telephone call. After that Loo turned to the park officials and said to them he was sorry, before running to jump down the cliff. The park officials were shocked. It happened so suddenly that they could not stop him.
The park officials returned to their office and went to Ao Nang police station to file a complaint before contacting rescue units in the area to launch a search for Loo.
The fate of the German tourist was still unknown, Mr Teekhawut said.
The 3.7km nature trail on the Khao Ngon Nak mountain, about 500 metres above the means sea level, is popular to adventure-loving tourists.
If you or anyone you know is in need of emotional support and counselling, please contact the Samaritans of Thailand at their 24-hour hotline 02-113-6789 (English & Thai) or the Thai Mental Health Hotline at 1323 (Thai).