Does the time difference between Bangkok and Manila change during the year?

No. The gap stays at 1h all year.

When is the best time to call Manila from Bangkok?

Between 09:00 and 16:00 in Bangkok, which is 10:00 to 17:00 in Manila.

Bangkok is 1h behind Manila. This gap is the same all year — neither city shifts its clocks relative to the other.

Bangkok

Thailand

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Manila

Philippines

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A 9-to-5 day in each city overlaps for 7h. That is 09:00–16:00 in Bangkok, which is 10:00–17:00 in Manila.

City	Time zone	UTC offset
Bangkok · Thailand	Asia/Bangkok	UTC+7
Manila · Philippines	Asia/Manila	UTC+8

What is the time difference between Bangkok and Manila?: Bangkok is 1h behind Manila. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Bangkok and Manila change during the year?: No. The gap stays at 1h all year.
When is the best time to call Manila from Bangkok?: Between 09:00 and 16:00 in Bangkok, which is 10:00 to 17:00 in Manila.