Both are running in Zone 6.

The two party chiefs not standing candidates on the party list are Chart Thai leader Banharn Silpa-archa and Puea Pandin leader Suvit Khunkitti, who will run in Suphan Buri and Khon Kaen respectively.

The proportional representation system consists of eight clusters of provinces nationwide and each cluster will be represented by 10 MPs.

In Zone 6, the main contest is likely to take place between the Democrat team, which includes Charoen Khanthawong and M.R. Sukhumbhand Paribatra, and the PPP pack which also comprises Chalerm Yubamrung, former MCOT director Mingkwan Saengsuwan and former Thai Rak Thai member Jatuporn Prompan.

Ruam Jai Thai Chart Pattana party leader Gen Chettha Thanajaro leads party-list candidates contesting Zone 5 which is likely to be another highly-charged election scene.

He is pitted against Pracharaj leader Sanoh Thienthong, Chart Thai member Akapol Sorasuchart, Democrat member Kraisak Choonhavan and PPP member Viroon Techapaiboon.

The seats in Zone 5 provinces, which include Nakhon Ratchasima, Pathum Thani, Sa Kaeo and Chon Buri, are likely to be split between Chart Thai, Democrat, PPP, Pracharaj and Ruam Jai Thai Chart Pattana.

Zone 1, which covers the provinces in the Upper North, is likely to be an easy win for PPP candidates, most of whom are former Thai Rak Thai MPs.

Prominent candidates include Yongyuth Tiyapairath, Somchai Wongsawat, Sompong Amornwiwat, Karn Thienkaew and Samphan Lertnuwat.

Mr Samak, meanwhile, was upset yesterday when Channel 9 tried to interview him and Mr Abhisit on the same programme.

He also said there was nothing wrong with the PPP being a nominee of deposed leader Thaksin Shinawatra.

''This is a battle of thoughts. There is nothing wrong with being a nominee of Mr Thaksin.

''And if the PPP gets a mandate to form a government, Mr Thaksin will return and fight the charges in court,'' he said.

Mr Samak also shrugged off the Chart Thai leader's rejection of moves to form a coalition government with the PPP.

''Mr Banharn will regret tying himself to the Democrat party,'' he said.

Mr Banharn yesterday reaffirmed the party's alliance with the Democrat party, saying Chart Thai would not be treated as an ''equal'' if it allied with the PPP.