We believe Thai Oil has a highly strategic status within the PTT group, and we see an extremely high likelihood of extraordinary government support for the PTT group in the case of financial distress. We believe the improvement in Thai Oil's credit quality underpinned by lower leverage in 2015 is sustainable over 2016-2017. We are revising upward our assessment of Thai Oil's stand-alone credit profile to 'bbb-' from 'bb+'. We are affirming our 'BBB' long-term corporate credit rating and our 'axA' ASEAN regional scale rating on the Thailand-based refinery-and-petrochemical company and our 'BBB' long-term issue rating on its senior unsecured notes. The stable outlook reflects our opinion that PTT group's credit profile and Thai Oil's group status will remain unchanged