Naming your baby by day of birth: the complete guide

Choosing a child's first name is one of the most carefully weighed decisions Thai parents make — the name is believed to stay with the child and shape their life. And in Thai tradition, an auspicious name doesn't start with meaning alone; it starts with the child's day of birth.

This guide covers it from the ground up: why the birth day matters, how the Thaksa-Pakorn system works, which letters to use and avoid on each day, and how to find your baby's true birth day from the due date — with real, usable name examples.

Why the birth day decides the name

In Thai astrology each weekday is tied to a ruling planet with its own energy. Thaksa-Pakorn takes this and sorts every Thai consonant into eight groups; the birth day then determines which groups are auspicious and which is 'kalakini' — the letters to avoid.

What many don't realise: Thai astrology splits Wednesday into two — Wednesday-day and Wednesday-night (called Rahu) — so there are actually eight naming buckets, not seven. Each has its own kalakini set.

How to find the birth day from a due date

If the baby isn't born yet, start from the estimated due date (EDD) and see which weekday it falls on. Crucially, if it's a Wednesday you also need the time: before 18:00 counts as Wednesday-day, and from 18:00 onward is Wednesday-night (Rahu) — which uses a different letter set entirely.

The birth-day calculator on the DekDuangDee home page does this automatically — enter the due date (and time if known) and it resolves the day and takes you straight to the matching name list.

The letters to avoid, day by day (kalakini)

The table below summarises each birth day's kalakini letters. If a name contains even one of them, tradition considers it inauspicious for someone born that day. Note Monday stands apart — its kalakini set is (almost) all the vowels, not a consonant group.

What about the 'good' letters? The 7 auspicious houses

Tāksā doesn't only say what to avoid — it sorts the remaining letters into seven auspicious houses, each with its own domain: Decha (power & honour), Si (glory & wealth) and Montri (mentors & support) are the three traditionally prized most.

So a good name isn't merely 'kalakini-free' — it also leans on these auspicious houses. The more a name draws on a prized house, the more it's said to reinforce that area of life. Each name's detail page on this site shows exactly which houses it leans into.