PTT Exploration and Production, the subsidiary of PTT, may be still holding out its bid for Mozambique-focused oil and gas explorer Cove Energy, but one analyst says the acquisition is a bad idea for the Thai oil company because it would hurt its balance sheet.

"It's (PTT) biting off more than it can chew, and I would prefer it to do smaller deals. We think already that PTT has a reasonably constrained balance sheet and that by doing this, the funding of the development puts more strain on the balance sheet," Scott Darling, Head of Oil and Gas Sector Research at Barclays, told CNBC Asia's “Cash Flow” on Wednesday.