% APNIC found the following authoritative answer from: whois.apnic.net

% [whois.apnic.net]
% Whois data copyright terms    http://www.apnic.net/db/dbcopyright.html

% Information related to '136.228.129.0 - 136.228.129.255'

% Abuse contact for '136.228.129.0 - 136.228.129.255' is 'abuse@sinet.com.kh'

inetnum:        136.228.129.0 - 136.228.129.255
netname:        SIGROUPS-KH
descr:          SINET, Dedicated Fiber, Dedicated Speed, Dedicated Support, Dedicated Always.
country:        KH
admin-c:        TP288-AP
tech-c:         DK804-AP
abuse-c:        AS2459-AP
status:         ALLOCATED NON-PORTABLE
mnt-by:         MAINT-KH-SIGROUPS
mnt-irt:        IRT-SPLUS-KH
last-modified:  2020-07-20T09:48:28Z
source:         APNIC

irt:            IRT-SPLUS-KH
address:
address:        Phnom Penh
e-mail:         abuse@sinet.com.kh
abuse-mailbox:  abuse@sinet.com.kh
admin-c:        TP288-AP
tech-c:         DK804-AP
auth:           # Filtered
remarks:        abuse@sinet.com.kh was validated on 2025-12-08
mnt-by:         MAINT-KH-SINET
last-modified:  2025-12-10T01:41:37Z
source:         APNIC

role:           ABUSE SPLUSKH
country:        ZZ
address:
address:        Phnom Penh
phone:          +000000000
e-mail:         abuse@sinet.com.kh
admin-c:        TP288-AP
tech-c:         DK804-AP
nic-hdl:        AS2459-AP
remarks:        Generated from irt object IRT-SPLUS-KH
remarks:        abuse@sinet.com.kh was validated on 2025-12-08
abuse-mailbox:  abuse@sinet.com.kh
mnt-by:         APNIC-ABUSE
last-modified:  2025-12-08T02:42:37Z
source:         APNIC

person:         Diep Kong
address:        #93, Preah Sihanouk Blvd
country:        KH
phone:          +855 81 927 999
e-mail:         kong.d@sinet.com.kh
nic-hdl:        DK804-AP
mnt-by:         MAINT-KH-SIGROUPS
fax-no:         +855 23 215 577
last-modified:  2018-04-18T03:01:13Z
source:         APNIC

person:         Tsiferana PEDERSEN
address:        S.I Building
                #93 Preah Sihanouk Blvd
country:        KH
phone:          +855 23 210 586
e-mail:         pedersen.r@sinet.com.kh
nic-hdl:        TP288-AP
abuse-mailbox:  abuse@sinet.com.kh
mnt-by:         MAINT-KH-SIGROUPS
last-modified:  2011-09-02T07:45:15Z
source:         APNIC

% Information related to '136.228.129.0/24AS131207'

route:          136.228.129.0/24
origin:         AS131207
descr:          S.I Group
                S.I Building
                #93 Preah Sihanouk Blvd
mnt-by:         MAINT-KH-SIGROUPS
last-modified:  2021-05-27T07:24:36Z
source:         APNIC

% This query was served by the APNIC Whois Service version 1.88.34 (WHOIS-AU4)