Just back from another trip to Nam Nao National Park and nearby areas in north central Thailand. There were nine of us on this trip (Martin, Ivan, Paul, Tiggy, Phil, Geraldine, Dave O, Fig and Floyd), the most we've had on a visit to Thailand since the April 2003 Umphang expedition. The plan had been to finish the surveying at the end of the 1992 Series in Tham Yai Nam Nao. However, we were thwarted on the very first trip as CO2 levels were so high the air was unbreathable just after the show cave. Our attention then turned to the Tham Phaya Naak area which is 1½ hours walk into the forest. The three caves here: Tham Wim Mahn Mak at the top, Tham Nop Pa Krauw in the middle, and Tham Phaya Naak at the bottom, where linked together via a single large shaft. The provisional length and depth of the system is 1,250 m long and 118 m deep. A new GPS fix on Tham Bahn Dahn, a stream cave lower than Tham Phaya Naak, has resulted in this cave being 'moved' under the Tham Phaya Naak system. There are high rifts in Tham Bah Dahn were it passes under the other cave and a link would add around 800 m to the length and 45 m to the depth. As Tham Yai Nam Nao was blocked by the CO2 'sump' Cave 14 was looked at. This was an undescended shaft located over the start of the 1992 Series. The shaft was rigged and some low, muddy crawls pushed through to the main cave adding about 150 m to the length of Tham Yai Nam Nao bringing it to 9,867 m. There were numerous forest walks, particularly to the area around Tham Phaya Naak. A stream cave was found below Tham Bah Dahn which wasn't explored as a handline was required to descend a wet climb and another stream cave was found about 1 km beyond Tham Phaya Naak where the exploration was soon stopped by a low, draughting duck. After New Year most of the team moved over the mountains from Lom Sak to Chumphae to be nearer the Pha Phuang Wildlife Sanctuary and Phu Pha Man National Park which were to be the focus for the middle third of the trip. With permission of the Pha Phuang boss we had a trip to Tham Singh Toh accompanied by some rangers. The large chamber was photographed and the 'right hand series' was pushed down some climbs and through some squeezes. The passage could be seen to level off, but the explorers ran out of time and this extension was not surveyed. Unfortunately we did not get permission to have a second trip in this cave to continue the exploration. In the nearby Phu Pha Man National Park the Tham Phaya Nakarat 'show cave' was surveyed to a length of 700 m and Tham Phra, near the well-known Bat Cave, was also looked at, but no major extension was made. Various other small caves were visited in the park, guided by a monk. After the hard caving and walking the expedition moved south to the seaside resort of Cha-Am. Visits were made to a waterfall in the Kaeng Krachan National Park as well as to Tham Kaeo and Tham Phaya Nakhon in the Khao Sam Roi Yot National Park. Only Ivan and Martin were left after the coastal visit and they returned to Lom Sak. In the following week various caves were looked at in Phetchabun and Loei provinces. These included Tham Pha Thong near Chon Daen which surprised us as it turned out to be 600 m long with large phreatic passage despite being in an isolated limestone tower. The other caves were the usual small temple jobs. In conclusion there is still plenty of work and leads left in the Tham Yai Nam Nao area, but after 3 consecutive years of visiting this area we are not sure when we will return.