Drought or something else?

[Bonsai Phill]

I have a Japanese Maple that I have been growing and developing from a seedling for about 25+ years, but this year it suddenly did this (see photo). Due to not having a garden myself, I keep my trees at my Dad's bungalow. He waters them for me and I do all the pruning and feeding when I go there on Sundays. He does, however, have a few mobility issues, and this may affect how any times he's able to go outside to water.
He said he thought it was frost damage because I watered the trees, having not realised we were going to have a hard frost that night (the last hard frost I think in the Midlands). I sent these photos to Greenwood Bonsai nursery where I bought it as a seedling, who said it looked as though it was drought damage due to the dying vegetation in the pot, and the compost receding from the sides of the pot. My Dad did say that during the following warm spell, he was only watering every 2 days, not taking into account the unseasonably warm Spring. If it2 is drought damaged, short if continuing to water it thoroughly, what else would you recommend to potentially save this tree, if it actually can be saved, that is?

 

[NeedlesAndLeaves]

Sad thing.. I would remove all the affected leaves. Hopefully the roots are not damaged so the tree can push out a second flush.
Keep an eye on the watering as much as possible in your situation.

 

[Shibui]

Hard to be positive without a closer look at the leaves, shoots and soil but I'd agree with dehydration.
Getting enough water into the pot becomes harder every year the tree is not repotted because roots gradually fill all the available spaces in the soil, leaving no room for water to penetrate. If this is the case, you may need to water more effectively or maybe soak the pot every week or 2 to make sure enough water soaks into the interior of the root ball for the rest of the Summer.

First aid for drought affected trees is to thoroughly soak the entire pot for a few hours or overnight. Best to dunk the entire pot into a tub of water because dry soil is notoriously difficult to re-wet.

Burnt leaves will usually fall off naturally but no problem cutting them off if you have the time and patience. I usually take the opportunity to trim any long shoots. I can see some really long internodes on some of the branches so I'd remove some or all of those too.
Provided the tree received water before the damage went too far, you should see new buds emerge from many of the nodes in 3-5 weeks.

 

[rockm]

When you take photos in life photos of the pot and soil. They’re the foundation for everything above. What shows up in the leaves starts at the roots usually.

This looks like the soil dried out substantially if not completely. Follow shibui’s advice on possible recovery. The tree may not be gone completely. Leave the leave alone in removing them you may inadvertently remove viable leaf buds at their bases. Probably a long shot but there might be some at this point

 

[Bonsai Nut]

Looks to me like a hard drought. Remove the crisped leaves and put the tree in total shade and water sparingly until it pushes new growth. Make sure you don't overwater (since the tree is using much less water now) and don't move into sun until any new growth has hardened.

FWIW I would recommend getting a sprinkler timer and drip irrigation system. Standard timers here in the US cost about $30. A "smart" timer that you can control over WiFi is a little more expensive at about $50. A WiFi sprinkler with a WiFi security camera and you can turn your water on and off - and see it happen - from anywhere you can get a WiFi signal. In most cases it costs less than a single tree.