Possible hole-in-head?

[Marshall]

Housing
What size is your tank? 5 Gallon
What temperature is your tank? Tropic temperature (singapore)
Does your tank have a filter? No
Does your tank have an air stone or other type of aeration? Airstone
Is your tank heated? No
What tank mates does your betta fish live with? No

Food
What type of food do you feed your betta fish? Pellet
How often do you feed your betta fish? once/twice a day. (3pellet)

Maintenance
How often do you perform a water change? 2 week
What percentage of the water do you change when you perform a water change? 100%
What type of additives do you add to the water when you perform a water change? Aqua-Safe Anti-chlorine

Water Parameters:
Have you tested your water? If so, what are the following parameters?
Not Tested

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? A few more missing scales or holes in head.
How has your betta fish's behavior changed? Normal
When did you start noticing the symptoms? 4 weeks ago.
Have you started treating your fish? If so, how? No
Does your fish have any history of being ill? No
How old is your fish (approximately)? 1year

This are the pictures i took. Im curious if this is hole-in-head.

[Sakura8]

I can't say for sure if it's Hole-in the Head (doesn't look like it to me) but it does look as if your betta may have "popeye." Do you change the water 2 times a week or once every 2 weeks?

[DarkMoon17]

It doesn't look like hole-in-the-head disease to me, but I agree with Sakura. Your betta has a mild case of popeye (left eye).

A few suggestions:
You need a heater, bettas are tropical fish and temperatures lower than 78* will lower their immune system to the point where they cannot fight off infections and results in lethargy and etc...

If you are only changing his water once every 2 weeks, then you need to increase water changes. You should be doing water changes weekly at the very least.

Pop eye is caused by poor water conditions, to cure it before it gets worse, increase water changes to 50% every 2-3 days. If you don't see improvement, you can treat him with aquarium salt. But increased water changes should do it. A heater would also speed up his recovery and would make him a very happy betta.

[Marshall]

I see. I do 50% change for 1 week, 100% change on 2 week. Will increase the water change. Thanks!
I was worried because i spotted tat the betta's head is not entirely white. didt realize it has popeye!

[Sakura8]

He's a beautiful betta, I love his coloring. Keep us posted on his recovery.