You've already answered your own question - what you are proposing isn't logistically viable. And - excuse me for being blunt - for a 'group executive chief' you are disturbingly unaware of the simplest of realities.
You need to be on the ground, as in actually living there/here, to be able to chase down a small house; an apartment or condo isn't an option with three cats. This is an ongoing activity which you need to be actively engaged in, with a daily ritual of scanning FB groups, looking through online rental sites, calling estate agents and travelling around looking at potential properties until you find what you want. And you simply can't come here on spec, to a temporary studio apartment while you look, with three cats.
But you need to be able to work - and by the sound of it would like to have already secured a position prior to going to Vietnam. On the other hand you are realistic enough to realise that the kind of executive post you currently hold is rare and that it's not tenable to expect to find something similar. But you have no idea what work is available, in which of the industries, or 'who to contact' about it. You don't even know what part of Vietnam you are heading for. Have you even checked out Vietnam's immigration policy and what type of visas are open to you and what they cost?
Have you taken into account that half of the country gets what amounts to a 6-month rainy season with a full monsoon in the middle of it?
Or that Vietnam is a nation of dogs which vastly outnumber cats?
That you will need private insurance or a medical plan? Or that pharmacies here will offer brand-names you're not familiar with?
How are you going to access the money you have in a South African bank - particularly when you need a large lump sum, such as paying nine month's rent up front or paying for a motorbike? Are you aware that ATMs in Vietnam mostly have a 2 million dong ($85 US) withdrawal limit?
Or that, without a work permit or an employer, as a South African you will have to stay here on a 3-month tourist visa and keep leaving the country and re-entering with a new visa?
There are only two possibilities - one is that you apply internationally for a management position with a company advertising a post in Vietnam. And the other is to come and live here for 3 or 6 months (to include the rainy season) so that you can discover more than you would on a brief holiday, and find out the answers to your very nebulous questions for yourself.
(Before I finally came to live in Vietnam I spent 18 months non-stop - every spare hour - researching the whole thing - finding out what the climate was like in different parts of the country; checking out the cost of electricity and discovering that there are different pricing strategies for private housing and apartment blocks, and what these costs were; joining all the local Facebook community sites in each of the major cities and scanning the posts every day; joining the property agents' FB groups or websites to check on what was available and the prices; researching the way in which taxis worked in the different cities and checking out comparative costs to get across town in the daytime and at night; studying the cities of my choice via Google Maps to see the layout and what major supermarkets/hypermarkets there were, and what international restaurants and what imported food; walking around the streets of my cities using Street View to see what things looked like at ground level. I would recommend doing this yourself, and asking questions (such as this one) as your knowledge grows!)
And I really can't think of a way that three cats and a 5-day working week with short hours fits in to any of it, although I wish you the very best of luck!