How to load data type fixed width support thai language

It looks like the issue is that the data in the file is not the same size as the columns you have defined in the COPY command.
To fix this, you will need to adjust the colsizes parameter to match the actual size of the data in the file.

Try this:

SELECT 'A1 char(4)' as DataType, OCTET_LENGTH('9999'), '9999' as Data
UNION ALL
SELECT 'A2 varchar(36)', OCTET_LENGTH('Aเจ้าหน้าที่ A'), 'Aเจ้าหน้าที่ A'
UNION ALL
SELECT 'A3 char(1)', OCTET_LENGTH('X'), 'X'
UNION ALL
SELECT 'A4 char(4)', OCTET_LENGTH('999 '), '999 '
UNION ALL
SELECT 'A5 char(4)', OCTET_LENGTH('XXXX'), 'XXXX'
UNION ALL
SELECT 'A6 char(4)', OCTET_LENGTH('2022'), '2022'
UNION ALL
SELECT 'A7 char(4)', OCTET_LENGTH('1214'), '1214';
--     DataType    | OCTET_LENGTH |    Data
-- ----------------+--------------+------------
--  A1 char(4)     |            4 | 9999
--  A2 varchar(36) |           36 | Aเจ้าหน้าที่ A
--  A3 char(1)     |            1 | X
--  A4 char(4)     |            4 | 999
--  A5 char(4)     |            4 | XXXX
--  A6 char(4)     |            4 | 2022
--  A7 char(4)     |            4 | 1214
-- (7 rows)

drop table if exists ABC cascade;
create table ABC (
A1 char(4),
A2 varchar(36),
A3 char(1),
A4 char(4),
A5 char(4),
A6 char(4),
A7 char(4));

COPY ABC( A1,A2,A3,A4,A5,A6,A7)
from STDIN
FIXEDWIDTH colsizes(4,36,1,4,4,4,4)
ENFORCELENGTH
ABORT ON ERROR;
9999Aเจ้าหน้าที่ AX999 XXXX20221214
1234Aเจ้าหน้าที่ A11234123412341234
\.

SELECT * FROM ABC;
--   A1  |     A2     | A3 |  A4  |  A5  |  A6  |  A7
-- ------+------------+----+------+------+------+------
--  1234 | Aเจ้าหน้าที่ A | 1  | 1234 | 1234 | 1234 | 1234
--  9999 | Aเจ้าหน้าที่ A | X  | 999  | XXXX | 2022 | 1214
-- (2 rows)

Another option would be to try using a delimited format for the data instead of fixed width. This would allow you to specify the data type for each column without needing to worry about the exact size of the data in the file. For example, you could use the following COPY command to load the data using a delimited format:

COPY public.ABC ( A1,A2,A3,A4,A5,A6,A7)
FROM local '/data/sampledata.TXT'
DELIMITER ','
REJECTED DATA AS TABLE public.ABC_RJCT
ENFORCELENGTH;

In this case, you would need to make sure that the data in the file is properly delimited using commas (or whatever delimiter you choose). You would also need to adjust the data types for each column to match the data in the file.

I hope this helps!