4 Rules in "Overtaking" Slower-Moving Vehicles

Overtaking or passing is the act of one vehicle going past another slower moving vehicle, travelling in the same direction, on a road. https://en.wikipedia.org/wiki/Overtaking

Section 39. Overtaking a vehicle. - The driver of any motor vehicle overtaking another vehicle proceeding in the same direction shall pass at a safe distance to the left thereof, and shall not again drive to the right side of the highway until safety clear of such overtaken vehicle except that on a highway, within a business or residential district, having two or more lanes for the movement of traffic in one direction, the driver of a vehicle may overtake and pass another vehicle on the right. Nothing in this section shall be construed to prohibit a driver overtaking and passing, upon the right, another vehicle which is making or about to make a left turn. (Land Transportation and Traffic Code; R.A. 4136)
NOTES:

[1] As a rule, overtaking must be performed to the left of the vehicle sought to be overtaken.
[2] Driving back to the right (merging) should be done only when it is safe and clear.
[3] Passing on the right is allowed in business or residential district with two or more lanes.
[4] Overtaking and passing on the right is also allowed when the vehicle in front is making or about to make a left turn.

MORE RULES:

DRIVER TO GIVE WAY TO OVERTAKING VEHICLE
https://www.projectjurisprudence.com/2018/07/driver-to-give-way-to-overtaking-vehicle-land-transportation-traffic-law.html

RESTRICTIONS ON OVERTAKING AND PASSING
https://www.projectjurisprudence.com/2018/07/restrictions-on-overtaking-and-passing-ra-4136-land-transportation-traffic-code.html